I've never played an alto clarinet. What are they like to play? Are they difficult to voice in the clarion like a bass? Even great bass clarinettists, in the upper registers, often sound like they are on the verge of squeaking. The alto doesn't seem to have that sound.
Regard my comments as novice observations after just two weeks with an instrument that is a restoration in progress.
I'm enjoying getting a work out on that Harry Pedler alto now. It's easy in the low register, a bit more challenging in the clarion. It could need a few new pads, and I'm still working out which mouthpiece works with which reed.
It's mostly open hole and that's not an issue. In fact it might fit me better than a Bb soprano. It's the only alto I have played, so not much of a basis for comparison. The rings are a great design for it being perfectly flat to the tone hole tops. It is easily played with the broad flat part of the fingers as opposed to the tips. The glissando technique works well but I noticed that I could even use the c hole plateau in a glissando by sliding off of it.
It's the first time I've customized reeds to improve response. I've been spoiled by consistent success with LaVoz mediums on everything.
That might have worked, but several 1.5 Vandoren reeds came with the mouthpiece(s) and those were way too limber, so I tried some NOS Rico # 3;- great quality cane but too stiff. So I've worked a few of the Ricos down at the heel, and I am getting pretty good sound all the way up.
That transition area between the manual registers is a bit fuzzy, just like with the bass Harry. At least with these being manual, I get to choose which one. One some notes hitting both results in split tones like that sax note in "Low Spark of High-heeled Boys". That could be useful?

The clarion response is better after tweaking the reeds, but I suspect a few of the old dried out pads don't seal completely. A few are newer. The altissimo is better, which seems to point to leaks. It has improved or maybe I have. Playing it might be softening up these old pads.
It does handle very similarly to the bass Harry Pedler, which I am used to, except the bass is definitely in need of the peg. The alto is very slightly heavier than my typical grenadilla Bb soprano. Sitting, I find that I can cradle the bell between my knees and it sits at the perfect position. Standing, I like having the strap and the thumb pad and it can rest against either leg.
Going to larger clarinets reminds of old film camera formats. Parameters that are insignificant with a smaller device become problematic as the device gets bigger and the solutions tried might be diverse. For that reason, basses and altos tend to be quirky compared to sopranos.
What surprised me, and it might be improved, but the low clarion notes have a distinctly saxophone like tone. All altos might not be like that and this one might be different with new softer pads.
I'm going to learn to play it and see what it is like in ensembles. I'm glad I took a chance on a mostly open hole model because I'm sure I can easily manage it. Just for kicks I tried it with parade gloves and the low register played just fine.
When I say that these are quirky, it's mostly the result of the plateau strategies. This one has two relatively neutral plateaus, the left thumb and the c (L3) hole. The result is that some fingering alternatives are in order in places. This one has it's own "rules" that diverge from the typical ones we use on a soprano. And the bass is all plateau, so another set of exceptions in fingering apply to it. One has to have some fingers down to hold onto the instruments, and these need to be neutral or helpful to the tone and pitch character.
Switching from one size to the others is helpful in understanding the principles that apply to all clarinets, or at least it is for me.
For the added versatility, I think an alto could be a very useful addition, particularly in small ensembles. It's a lot of range in a small package.